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Big Meteoroid Boomerangs Around Earth

For the first time ever, a meteor has grazed in and out of Earth's atmosphere, slowing enough to become a temporary satellite that perhaps lasted a full orbit.

By evening on September 21st, an earlier storm had moved eastward and left skies over the British Isles beautifully clear.

Martin Goff, an officer with the Greater Manchester [England] Police, was making his rounds when he spotted a dazzling meteor at 22:55 p.m. (21:55 Universal Time). "I immediately pulled the van over to better see the fireball," he recounts. "Although not an experienced astronomical observer I was able to log relevant information such as altitude and azimuth relative to the straight road I was on and to trees and streetlights nearby." He estimates it was about as bright as a full moon and remained visible for 35 to 40 seconds, fragmenting for at least the last half of that. "I was just flabbergasted to have seen it!"

Lucky skygazer Damien Stenson was photographing O'Briens Tower at Ireland's Cliffs of Moher when a brilliant, fragmenting bolide passed behind. Stenson used LEDs to illuminate the tower in this 30-second exposure. Click on the image for a larger version.

He was hardly alone in his amazement. Friday-night crowds were out and about when the bolide appeared, delighting and amazing untold thousands as it broke into dozens of pieces as it glided east to west across the sky. Dirk Ross, who tracks bright meteors and meteorite finds worldwide, logged 564 eyewitness reports from England, Scotland, Ireland, France, Belgium, The Netherlands, and Norway.

A few hours later, Ross received another burst of 126 sightings. But these weren't from Europe — instead, a fireball had appeared over southeastern Canada and the U.S. Northeast. What at first seemed the unlikely arrival of two dramatic bolides in a single night might turn out to be something much more historic and scientifically profound.

Mathematician Esko Lyytinen, a member of the Finnish Fireball Working Group of the Ursa Astronomical Association, has analyzed the European sightings and concludes that the two events resulted from a single large body grazed the upper atmosphere, dipping to an altitude of 33 miles (53 km) over Ireland before escaping back to space. Because it arrived moving at only about 8 miles (13 km) per second, barely above Earth's escape velocity, it lingered for more than a minute as it crossed the sky. (This explains why some witnesses mistook it for reentering spacecraft debris.)

Dynamicists believe a large meteoroid broke apart as it passed over Ireland on the night of September 21, 2012. Slowed by its atmospheric passage, the object entered a temporary orbit around Earth and returned to the sky over eastern North America 155 minutes later.

S&T: Kelly Beatty

Lyytinen says the brief atmospheric passage took its toll. As the meteoroid broke apart, its velocity dropped to just 5.7 miles (9.2 km) per second, too slow to make an escape back to space. Instead, it became a temporary satellite of Earth, looping completely around the globe before reentering the atmosphere — this time for good.

A second analysis of photos and videos of the European event, by aerospace engineer and meteor expert Robert Matson, likewise suggests that a big chunk of this Earth-grazer ended up in a temporary orbit with an inclination of about 54° (corresponding to the latitude of its "perigee" over Ireland). Its single looping orbit was highest, about 3,930 miles (6,330 km), somewhere south of Australia, before it boomeranged back to a fiery finale.

However, after a close look at the event over North America, Matson is now skeptical that it's related to the earlier graze seen across the Atlantic. "Using two all-sky videos from Ontario, Canada, I was able to roughly triangulate the location of the Québec fireball to a spot between Ottawa and Montréal," he says. "Unfortunately, I cannot dynamically link this location and timing with that of the U.K. fireball — it is too far west." Moreover, Matson adds, the videos show a fairly short-duration event and a much steeper trajectory than a UK remnant could have had.

A subsequent analysis by John Mason and Nick James of the British Astronomical Association likewise argues against the two fireball events being related. They calculate that the brightest fragments seen over the U.K. exited the atmosphere with velocities of 5.3 and 4.9 miles (8.5 and 7.8 km) per second, too slow to send them looping around Earth.

There've been widely seen grazers before, though nothing quite like this. On the evening of October 9, 1992 (also a Friday, by the way), thousands witnessed a bolide that broke apart as it screamed up the East Coast. A piece of it struck a parked car in Peekskill, New York. An even larger meteoroid streaked across the Rocky Mountain sky in broad daylight on August 10, 1972, coming as close as 35 miles (57 km) before returning to interplanetary space. (Its velocity was too fast to become captured.)

If the fireballs seen in North America and Europe are not part of the same event, then they were a remarkable near-coincidence. Lyytinen explains that getting a final determination will require close attention to several subtle factors: the object's angle as it exited the atmosphere over the Irish coast, how rapidly the fragments were moving apart from one another, and how the Coriolis effect (due to Earth's rotation) affected the trajectory. Large fragments of the original meteoroid could have reentered the atmosphere anywhere along the orbital track.

In any case, high-quality snapshots and videos from astonished onlookers have been key to piecing together the story of September 21st's double feature. For example, Ross has collected 31 videos of the meteoroid passing over Europe.

Photographer Damien Stenson was definitely in the right place at the right time with the right equipment, as he was taking long exposures of the stars and scenery along the Cliffs of Moher on Ireland's west coast. Two of his images are especially diagnostic — and beautiful — in that they clearly show the fragmenting object framed by the Big Dipper and other far-northern stars.

"I spend a lot of time out photographing the Milky Way, meteors, etc.," Stenson comments, "but this was the most impressive sight I've seen yet."

12 thoughts on “Big Meteoroid Boomerangs Around Earth”

Darn, I wish I had been looking skyward in a good place to see this meteor! You say this was the first time a meteor has ever grazed Earth’s atmosphere, temporarily achieved orbit, and reentered the atmosphere. What are the odds that this may have happened before we had a global communication network to immediately report and correlate observations on different continents? If a meteor enters Earth’s atmosphere twice but there’s nobody there to see it, does it create a fireball?

I remember a spectacular meteor shower during the ‘90s. There were several hundred per hour, long and bright. About 1 in 100, however, were moving the complete opposite direction, very conspicuously. After talking it over, we decided these rebels had approached Earth on the opposite side, and Earth’s gravity had forced them into a hard U-turn.

This isn’t the first time this has happened though. The first documented boomerang event reportedly occurred on the 8th October 1996 over Northern New Mexico. A fireball was seen entering the atmosphere and partially broke up, but skipped back out. Its encounter with the atmosphere was enough to slow its velocity such that it entered a temporary orbit, and about 100 mins later it re-entered the atmosphere, this time of the coast of California, where it then burned up in the atmosphere. Details can be found in the Paper Back version of Lewis Spence’s “Rain of Ice and Fire” (in the afterword), or in his other book “Comet and Asteroid Impact Hazards on a Populated Earth: Computer Modelling”.

Anthony wondered: "What are the odds that this may have happened before we had a global communication network to immediately report and correlate observations on different continents?" Yes, I think we can say "of course" to that. It has certainly happened before. It should be reiterated that it MAY NOT have happened this time (see the article). But it has happened before on a regular basis. The exact frequency depends on the size of the meteor. This was a big one. For objects in this size range (+/-50% by diameter), I would make a wild guess of once a decade for a skip entry like this in that size range. A skip entry where both the initial entry and the final entry are BOTH over populated areas –which is what this might possibly be– is probably ten times more unusual…

That meteor shower, described by Peter, with several hundred meteors per hour was presumably one of the Leonid storms. You mentioned occasional meteors going the other way. These are usually called "sporadics" and they’re not rare though they certainly stand out in the middle of a major meteor shower. They’re just "common" meteors that happen to occur during the shower. They’re not wayward members of the shower itself. The Earth’s gravity is insufficient to cause the "U-turn" that you suggested. In fact, the Earth’s gravity deflects a passing meteor in a meteor shower by only a few degrees since they are in relatively high speed orbits. And meteors in showers are always small objects which cannot experience the "skip" effect that a large meteor, like the one described in this article.

The lead to the article suggests that the object may have completed "perhaps a full orbit" before re-entering. This is dynamically impossible. The trajectory after the initial skip was necessarily "sub-orbital", like a ballistic missile. If an orbit below escape velocity intersects the Earth’s atmosphere (as we know this one did) on one side of the Earth, then it will necessarily intersect the Earth’s atmosphere less than one orbit later UNLESS it has received some additional impulse on the apogee side of the orbit. This is why spacecraft, like the now-retired Space Shuttles, fired their rockets briefly to "circularize" the orbit. This lifts the perigee back out of the atmosphere so that the spacecraft does not immediately re-enter less than one full orbit later. A natural object, like a meteor, could not get any such secondary impulse unless the object was volatile, like a comet, and just happened to "vent" gas on the apogee side of the orbit in a fashion that would mimic a rocket burn –highly unlikely. A double-sip is also a remote possibility, but highly unlikely in this case since the object was visually observed disintegrating into much smaller pieces (smaller bits experience significantly greater drag and would not skip back out).

We were hosting an Open House at our clubs observatory at Sleaford Observatory in Saskatchewan Canada on the 22nd and we saw many more meteors than ussual…..many more. So much so that someone commented it must be a new shower.
I wonder if this was the same event.

"The trajectory after the initial skip was necessarily "sub-orbital", like a ballistic missile. If an orbit below escape velocity intersects the Earth’s atmosphere (as we know this one did) on one side of the Earth, then it will necessarily intersect the Earth’s atmosphere less than one orbit later"

This asteroid was thought to graze earth’s atmosphere at 13 kilometers/sec which is 2 km/s higher than escape velocity. (Escape velocity at that altitude is about 11 km/s). It was thought to exist the atmosphere at around 9 km/s which is faster than circular orbit velocity (about 8 km/s).

If it had exited at escape velocity or higher, it’s path would have been parabolic or hyperbolic and it would not have returned.

With a speed greater than circular and and less than parabolic, it’s quite possible for an object to make a full circuit and return to its perigee.

I was looking on AF.net and I saw that people saw this fireball. I went out the same day and I saw another fireball and reading this showed me that I saw this fireball! A temporary satellite of earth! Now, I feel special.

@FER: The “reverse” meteors were definitely not sporadics. They were heading towards the radiant, were the same brightness, color and duration as those coming from the radiant. Earth’s atmosphere does not have an edge; it is a gradient. That “few degrees” gradually increases to many degrees as they come closer and closer to hitting Earth. There has to be some elevation, for any given particle size, at which the atmosphere would slow them just enough to go "sub-orbital" without burning up. Unlikely as this seems, only about 1 in 100 were seen going backwards. I can picture an upper size limit, above which no meteoroid can skip, but I’m not seeing the reason for a lower limit. The only way we’ll know for sure is if other observers at other showers report reverse meteors as well.